logic - same as common sense?

[bloody_capitalist_sham]

ive been reading the thread on dialectical materialism in learning, and they are talking about logic.

What are the different types of logic?

Which ones are the best and most widely used and why?

cheers all. *tip hat*

[Rosa Lichtenstein]

BCS, since the mid-19th century, dozens of new logics have been developed, which now means that 95% of logic is less than 150 years old.

The old Formal Logic of Aristotle is now only of interest to antiquarians (and, of course, DM-fans, who still to this day know nothing of these developments, no matter how many times they are told).

Something called 'classical logic' was developed by Frege, Peano, Russell and Whitehead (among others) in the years between 1879 and 1920, and completely revolutionised it (consigning the old logic to the stacks shelves in University libraries):

http://plato.stanford.edu/entries/logic-classical/

You would think this referred to the logic discovered in ancient Greece, but this would be a mistake; it is the logic most undergraduates in philosophy or mathematics have to learn.

Since then, dozens of other post-classical logics have been constructed: tense logic (the logic of inferences to do with time and change -- which alone makes a mockery of the claim that logic cannot handle change), modal logic (originally developed by Aristotle and other Greek Logicians -- it has to do with inferences to do with possibility and necessity), epistemic logic (related to knowledge and belief), deontic logic (related to ethical inferences), many-valuued logic (a logic that allows for other things over and above truth and falsehood), and many others.

http://plato.stanford.edu/entries/logic-temporal/

http://plato.stanford.edu/entries/logic-modal/

http://plato.stanford.edu/entries/logic-epistemic/

http://plato.stanford.edu/entries/logic-manyvalued/

http://plato.stanford.edu/entries/logic-deontic/

Common sense has nothing to do with logic, and you would be hard-pressed to find anyone who knows exactly what it is.

There are so-called 'Informal Logics' that deal with everyday reasoning, which is about as close as you get to a link between logic and common sense.

http://plato.stanford.edu/entries/logic-informal/

99% of this goes right over DM-fans heads, but still they pontificate on the subject.

On the revolutionary change that occured in the later 1870's in logic, a result of the work of Frege, see:

http://www.iep.utm.edu/f/frege.htm#H2

http://en.wikipedia.org/wiki/History_of_lo...of_modern_logic (http://en.wikipedia.org/wiki/History_of_logic#The_advent_of_modern_logic)

Hope this helps!

[bloody_capitalist_sham]

Thanks rosa, it helps alot.

Although the algebra is scary hehe.

Can i ask what logic you use?

Can you use them all in conjunction, as it seems that they are specific to different areas.

Are there any marxists who try to make sense of what marx and engles did with DM to try an create a kind of logical materialism. lol i dont know if that even makes sense though.

thanks for the post :).

[Rosa Lichtenstein]

You are right about the algebra, but algebra is much easier than logic, in my experience!

I was trained in classical logic -- but in a sub-branch of it called 'Natural Deduction':

http://en.wikipedia.org/wiki/Natural_deduction

I do not use logic as such now, since I am not an academic.

But, in my refutation of DM, I appeal to several logics, but mainly classical logic.

They all overlap somewhat, but they are all separate systems; and there are many forms of 'non-standard' logic that use different axioms/rules, or proof structures -- there are dozens of these; more details at:

(A) http://www.earlham.edu/~peters/courses/logsys/nonstbib.htm

And there is something called 'second order logic':

http://en.wikipedia.org/wiki/Second-order_logic.

As far as Formal Logic and DM are concerned, you can find some of my thoughts on this at:

http://homepage.ntlworld.com/rosa.l/page%2004.htm

There are some Marxists who accept modern logic, but who also think that Hegel and Engels were right to claim contradictions, for example, exist in reality (or better, that there are 'true contradictions'); these are the so-called 'Dialetheists' (who use something called 'Paraconsistent Logic' -- more details on link (A) above).

The leading figure in this 'movement' is Graham Priest, a master of modern logic, but also a Marxist, and a dialectician (!!).

So, he is a living disproof of the claim that modern logic (suitably modified) cannot be made compatible with DM -- contrary to what, say, Axel keeps alleging.

So, if there are any 'logical materialists', these are they!

Although, I would also call myself a logicl materialist (but not in the same sense!).

However, later on at my site, I will be posting my reasons why, even though I have great respect for his work, I think Priest is in error.

[JimFar]

I think that some Soviet philosophers would fall into the category of what you refer to as "logical dialectical materialists." For example, Dmitry Gorsky in his book, Generalisation and Cognition (Progress Books, 1985), suggested that certain aspects of dialectics could be modeled in terms of either Ackermann's relevance logic or in terms of Zadeh's fuzzy logic and fuzzy set theory (which Graham Priest, BTW, has said, constitutes a paraconsistent logic).

[Rosa Lichtenstein]

Jim, thanks for that; I am not familiar with Gorsky, and if I can get hold of a copy of his book, I will rectify that.

Ackermann I am familar with, but since I am a classical logician over, say, the nature of material implication, I do not go along with his work (as valid a formal system as it is in itself).